如何使用变量使用 latex2exp 注释 ggplot2 plot？

Question

Here is my sample code.

library(ggplot2)
library(latex2exp)
p1 <- ggplot(mtcars, aes(x = wt, y = mpg)) + geom_point()
alpha=10
beta=20
p1 + annotate("label", x = 4, y = 25, label = TeX("$y = alpha e ^{betax}$"))

I was trying to get a label like y=10e^{20x} . Is it possible with latex2exp or is there better way?

Thanks

Answer 1

Try TeX(paste("$y = ", alpha, "e ^{", beta, " x}$")) ?

Answer 2

One way to do it with latex2exp would be to use sprintf to construct the LaTeX string:

p1 + annotate("label", x = 4, y = 25, label = TeX(sprintf("$y = %d e ^{%dx}$", alpha, beta)))

Answer 3

You can use bquote() or paste() , and set the argument parse=TRUE

library(ggplot2)
p1 <- ggplot(mtcars, aes(x = wt, y = mpg)) + geom_point()
alpha=10
beta=20
p1 + 
  annotate("label", 
           x = 4, y = 25, 
           label = list(bquote(y==.(alpha)*e^{.(beta)*x})), parse= TRUE
  )

p1 + 
  annotate("label", 
           x = 4, y = 25, 
           label = paste("y==", alpha, "*e^", "{", beta, "*x}"), parse= TRUE
  )

^{Created on 2020-04-23 by the reprex package (v0.3.0)}

Hopes helpful for you.